The integrity of the intestinal epithelium is essential for the well-being of the organism throughout life. Alterations in the composition of the intestina microbiota have been implicated in various human disorders and are significantly correlated with measures of frailty, co-morbidity and inflammation in the elderly. However, fundamental questions remain regarding the relationships between intestinal integrity, aging, microbiome dynamics and organismal health and longevity. In preliminary work, we have shown that intestinal barrier dysfunction accompanies aging across a range of Drosophila genotypes and environmental conditions. Moreover, the age-dependent loss of intestinal integrity is tightly linked to dysbiosis of the intestinal microbiota as well as multiple markers of organismal aging, including systemic metabolic dysfunction, increased expression of immunity-related genes, and, critically, is a harbinger of death. These findings provide an important first step towards understanding the causal relationships between intestinal dysbiosis, intestinal barrier dysfunction, and organismal aging. AMP-activated protein kinase (AMPK) and the cellular recycling process of autophagy have each been linked to aging in diverse species; however, the tissue-specific mechanisms involved are poorly understood. Recently, we have shown that AMPK induces autophagy to delay the onset of intestinal barrier failure and promote longevity. These findings provide a framework to investigate how a key aging pathway (AMPK/autophagy) modulates pathophysiology to prolong healthy lifespan. Here, we propose to build upon these groundbreaking findings by exploring three broad questions: 1) What are the causal relationships between intestinal barrier dysfunction, intestinal dysbiosis, immunity gene activation and aging? 2) What are the causal relationships between intestinal barrier dysfunction, intestinal dysbiosis, systemic metabolic dysfunction and aging? 3) What are the causal relationships between AMPK/autophagy activation, microbiome dynamics, intestinal homeostasis and aging? The work described in this grant proposal will bring about fundamental knowledge towards our understanding of the molecular and cellular mechanisms of aging. At the same time, our findings may lead to new therapeutic approaches to treat age-related diseases in humans.